1. Field of the Invention
This invention relates to disk drive suspensions, and more particularly to wireless disk drive suspension assemblies having a flexible conductive laminate forming the electrical connection between the slider, including the disk read write element/head, and the suspension signal electronics. In a particular aspect, the invention provides an improved shunt for protecting the read write head during suspension assembly operations. The shunt structure is reusable and comprises in one embodiment a conductive material shunt structure carried on a conductive trace-free portion of the laminate insulative layer, suitably with adjacent adhesive for separably bonding the shunt structure to a further laminate insulative layer portion such as that which supports the conductive traces, the conductive material and adhesive being arranged such that the shunt structure is in shunting contact with the laminate conductive traces.
2. Related Art
One of the major problems with wireless suspensions is the occurrence of spontaneous electrostatic discharges (ESD) through them when they are connected to magnetoresistive (MR) disk read elements/heads or giant magnetoresistive (GMR) element/heads. Any external charge poses a risk of traveling to the MR or GMR element. Thus a charge from a person or from an insulating surface charge build-up can flow via the trace/wire leads (or pads) to the slider/head and damage the MR sensor element, sometimes melting the sensor element. It takes as little as 15 volts for a GMR head to be damaged. One of the ways to prevent this phenomenon is to connect all the leads in parallel so that this current does not pass through the MR element. Designing a circuit with a shunt across the leads before the head is attached to the suspension will connect the leads in parallel. But, this solution only is effective when the assembly of the wireless conductor and MR or GMR is in other than a test or operating condition. In a test or operating situation, after the head/element is attached to the conductors/traces to be tested for reading and writing to disk, the presence of the shunt circuitry prevents testing and the shunt needs to be removed. The shunt is cut-off from the remainder of the circuit and it cannot be reattached; electrostatic discharge protection no longer exists for the affected part although more handling and testing is required.
In U.S. Pat. No. 6,351,352, assigned to the assignee of this application, the disclosure of which is incorporated herein by this reference, a form of separably adherent shunt and method was disclosed. The method included protecting a disk head from spontaneous electrostatic discharge current during the assembly but not during the actual testing operations of a disk drive suspension comprising a load beam and a flexible conductive laminate. The laminate had at least one pair of trace conductors connected to the magnetoresistive head. Adjacent portions of the trace conductors comprising each conductor pair were exposed, and there was applied to the exposed trace conductor portions a separably adherent shunt structure to temporarily connect each the pair of trace conductors in parallel while there was a potential for a spontaneous electrostatic discharge current reaching the disk head, such that the discharge currents were directed away from the head.